Filter and ink-jet recording apparatus having the same

ABSTRACT

A filter, the alignment of which does not need to be adjusted, and an ink-jet recording apparatus having such a filter are provided, the ink-jet recording apparatus capable of avoiding leakage of residual liquids in filter exchange operation. The filter of the present invention includes an upper capsule member, a lower capsule member, and a filter medium. The upper capsule member has a central connecting port and a peripheral connecting port, and also has a pipe section that extends, within the capsule, from the peripheral connecting port to the vicinity of the bottom surface (the deepest section) of the lower capsule member. A liquid supplied from the peripheral connecting port via the pipe section is filtered through the filter medium, and the filtered liquid is output from the central connecting port.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 13/671,683, filed Nov. 8, 2012, which is a divisionalapplication of U.S. patent application Ser. No. 12/543,964, filed Aug.19, 2012, which claims priority from Japanese Application JP2009-141247, filed on Jun. 12, 2009, all of which are hereinincorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a filter and an ink-jet recordingapparatus having the same.

2. Background Art

In ink-jet recording apparatuses, ink stored in an ink container of themain body is pumped into a nozzle of an ink discharge head by a feedpump. During operation, ink is continuously discharged from a dischargeorifice of the nozzle and broken into particles. Among ink particlesdischarged from the nozzle, those used for printing areelectrostatically charged and deflected, and then land on a print mediumto form text thereon. Meanwhile, ink particles not used for printing arenot electrostatically charged or deflected, but travel into an openingof a gutter that is located along the direction straight ahead of thedischarge orifice of the nozzle, and are collected into the inkcontainer by a recovery pump for re-use purposes.

There are cases in which foreign substances adhere to the inner side ofthe discharge orifice of the nozzle or to the circumference thereofduring operation, whereby the direction of ink discharged from thedischarge orifice could change. In such cases, ink particles not usedfor printing could deviate from the opening of the gutter, therebycontaminating the inner side of the ink discharge head, productionfacilities, products, and the like, or the discharge orifice couldbecome clogged, thereby preventing ink from being discharged or printed.Examples of foreign substances include dust in air that is sucked intothe gutter during operation and dust in air that enters an ink supplyunit while ink is being supplied. Such dust will reach the nozzlethrough the channel of the ink. In order to remove such foreignsubstances, the ink-jet recording apparatus has a filter provided in thechannel upstream of the nozzle.

FIG. 1 illustrates an exemplary structure of a conventional filter. Asillustrated in FIG. 1, a conventional filter 700 includes a capsulemember 701 with a connecting port 711 and a capsule member 702 with aconnecting port 712 that are joined together in the form of a singlecapsule. Within the capsule is provided a cylindrical filter medium 703.One end face of the filter medium 703 is joined to the capsule member701 and the other end face thereof is joined to a cap member 704. Thetwo connecting ports communicate with each other through the filtermedium 703. The two connecting ports of the filter 700 face oppositedirections. Thus, there is a possibility that when the old filter isremoved for the purpose of being replaced with a new one in filterexchange operation, drops of ink remaining in the old filter couldcontaminate the surrounding area.

As a filter that solves the aforementioned problem, a filer having twoconnecting ports that face the same direction has been considered. FIG.2 illustrates an exemplary structure of such a conventional filter. Asillustrated in FIG. 2, a filter 500 has a top capsule member 501 withtwo connecting ports (i.e., a central connecting port 511 and aperipheral connecting port 512) and a bottom capsule member 502 that arejoined together in the form of a single filter capsule. One end face ofa cylindrical filter medium 503 provided in such a filter capsule isjoined to the capsule member 501 and the other end face thereof isjoined to a cap member 504. Since the two connecting ports of the filter500 face the same direction, there is an advantage in that it ispossible to reduce the possibility of contaminating the surrounding areawith ink drops by adjusting the orientations of the two connecting portssuch that they face upwards in removing the old filter in filterexchange operation.

FIG. 3 is a systematic diagram of an ink circulation system that usesthe filter 500. The filter 500 is disposed in a channel 680 between anink container 601 and a nozzle 651 with a feed pump 611 interposedbetween the filter 500 and the ink container 601. In addition, a branch641 leading to a channel 682 that communicates with a suction port of arecovery pump 613 is disposed in a channel 681 between the filter 500and the nozzle 651.

In removing the old filter in filter exchange operation, it is necessaryto remove the ink remaining in the filter in order to reduce thepossibility of contaminating the surrounding area with the ink. FIG. 4illustrates the flow of ink in removal of the ink. In FIG. 4, the inkcontainer is exposed to air. With such a flow, ink in the ink containeror ink channel is displaced by air so that the ink is discarded to theoutside of the apparatus. FIG. 5 illustrates the orientation of thefilter in removal of the ink. As illustrated in FIG. 5, the orientationof the filter 500 is set so that the two connecting ports thereof (i.e.,the central connecting port 511 and the peripheral connecting port 512)face the horizontal direction with the peripheral connecting port 512located on the lower side of the central connecting port 511. Ink flowsin the direction from the central connecting port to the peripheralconnecting port 512. Since the ink located above the peripheralconnecting port 512 of the filter during removal of the ink is displacedby air, almost all the ink can be discharged.

Meanwhile, after the ink is removed and the filter is replaced with anew one, it is necessary to remove air from the new filter. Removal ofair is necessary in order to prevent the residual air from flowing outof the filter and thereby reaching the nozzle during operation, whichcould otherwise cause ink splattering when it is discharged from thedischarge orifice, and thus could contaminate the inner side of the inkdischarge head, production facilities, products, and the like, or inkparticles may not be deposited onto a desired place, resulting inabnormal printing. FIG. 6 illustrates the flow of ink in removal of air.With such a flow, an ink channel is filled with ink of an ink supplyreservoir. FIG. 7 illustrates the orientation of the filter in removalof air. As illustrated in FIG. 7, the orientation of the filter 500 isset so that the two connection ports thereof face the horizontaldirection with the peripheral connecting port 512 located on the upperside of the central connecting port 511. Upon entry of ink into thecentral connecting port 511, air is discharged from the upper peripheralconnecting port 512. Thus, almost all the air in the filter can bedisplaced by the ink. [Reference 1] JP Patent Publication (Kokai) No.2004-230321 A

SUMMARY OF THE INVENTION

However, in ink-jet recording apparatuses that use the conventionalfilter 500, an operator needs to check the orientation of the filter 500or appropriately adjust the orientation of the filter 500 in a series ofoperations of replacing the filter 500. Thus, if the operator fails toadjust the orientation of the filter 500 or adjusts the orientation ofthe filter 500 in error, there is a possibility that the old filter maybe removed with ink still remaining therein, or the apparatus may beoperated with air remaining in the new filter, which can cause inkcontamination or abnormal printing. Although it is possible to provide amechanism that automatically adjusts the orientation of the filter, itwill increase the production cost of the ink-jet recording apparatus.

The present invention has been made in view of the foregoing, and it isan object of the present invention to provide a filter, the orientationof which does not need to be adjusted, and an ink-jet recordingapparatus having such a filter while reducing the possibility ofcontaminating the surrounding area in filter exchange operation.

In order to achieve the aforementioned object, the filter of the presentinvention includes an upper capsule member, a lower capsule member, anda filter medium. The upper capsule member has a central connecting portand a peripheral connecting port, and also has a pipe section thatextends, within the capsule, from the peripheral connecting port to thevicinity of the bottom surface (the deepest section) of the lowercapsule member. A liquid supplied from the peripheral connecting portvia the pipe section is filtered through the filter medium, and thefiltered liquid is output from the central connecting port.

The upper capsule member has on its inner side a dome-shaped topsurface, and the connecting port (the central connecting port) isarranged at the center of the dome-shaped top surface. Further, thelower capsule member has on its inner side a dome-shaped first bottomsurface section, a second bottom surface section (the deepest section)located opposite an end of the pipe section, and a channel connectingthe first bottom surface section and the second bottom surface section,the channel being adapted to guide the filtered liquid from the firstbottom surface section to the second bottom surface section. The channelof the lower capsule member has a sloped section leading from thecentral portion of the first bottom surface section to the second bottomsurface section.

The ink-jet recording apparatus of the present invention includes theaforementioned filter, a nozzle that discharges ink used for printing,an ink container in which the ink is stored, a feed pump that pumps theink to the nozzle, and a recovery pump that collects the ink into theink container. In addition, a branch leading to a channel thatcommunicates with a suction port of the recovery pump is provided in achannel between the feed pump and the filter. Further features of thepresent invention will become apparent from the following preferredembodiments for carrying out the present invention and the accompanyingdrawings.

According to the present invention, it is possible to eliminate the needfor adjusting the orientation of a filter in a series of filter exchangeoperations. Thus, the operator can save the effort of checking theorientation of the filter, and it is also possible to reduce thepossibility of ink contamination and abnormal printing that couldotherwise be caused due to the ink remaining in the old filter or theair remaining in the new filter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1 are an exploded perspective view and a cross-sectional view of afilter of a conventional ink-jet recording apparatus;

FIGS. 2 are an exploded perspective view and a cross-sectional view of afilter of a conventional ink-jet recording apparatus;

FIG. 3 is a systematic diagram of an ink circulation system of aconventional ink-jet recording apparatus;

FIG. 4 is a systematic diagram illustrating the flow of ink in removalof the ink from a filter of a conventional ink-jet recording apparatus;

FIG. 5 is a cross-sectional view illustrating the orientation of afilter of a conventional ink-jet recording apparatus in removal of inkfrom the filter;

FIG. 6 is a systematic diagram illustrating the flow of ink in removalof air from a filter of a conventional ink-jet recording apparatus;

FIG. 7 is a cross-sectional view illustrating the orientation of afilter of a conventional ink-jet recording apparatus in removal of airfrom the filter;

FIGS. 8 are an exploded perspective view and a cross-sectional view of afilter of an ink-jet recording apparatus in accordance with anembodiment of the present invention;

FIG. 9 is a systematic diagram of an ink circulation system of anink-jet recording apparatus in accordance with an embodiment of thepresent invention;

FIG. 10 is a systematic diagram illustrating the flow of ink in removalof the ink from a filter of an ink-jet recording apparatus in accordancewith an embodiment of the present invention;

FIG. 11 is a cross-sectional view illustrating the orientation of afilter of an ink-jet recording apparatus in accordance with anembodiment of the present invention in removal of ink from the filter;

FIG. 12 is a systematic diagram illustrating the flow of ink in removalof air from a filter of an ink-jet recording apparatus in accordancewith an embodiment of the present invention;

FIG. 13 is a cross-sectional view illustrating the orientation of afilter of an ink-jet recording apparatus in accordance with anembodiment of the present invention in removal of air from the filter;

FIG. 14 is a perspective view illustrating the external appearance of anink-jet recording apparatus in accordance with an embodiment of thepresent invention;

FIG. 15 is a perspective view illustrating the use state of an ink-jetrecording apparatus in accordance with an embodiment of the presentinvention;

FIG. 16 is a functional diagram of an ink-jet recording apparatus inaccordance with an embodiment of the present invention;

FIG. 17 is a flowchart illustrating the control operation in removal ofink from a filter of an ink-jet recording apparatus in accordance withan embodiment of the present invention; and

FIG. 18 is a flowchart illustrating the control operation in removal ofair from a filter of an ink-jet recording apparatus in accordance withan embodiment of the present invention.

DESCRIPTION OF SYMBOLS

-   1 main body-   2 ink discharge head-   3 operation display section-   4 conduit-   15 belt conveyor-   16 encoder-   17 print sensor-   100 ink-jet recording apparatus-   101 MPU-   102 ROM-   103 RAM-   104 input device-   105 output device-   111 excitation voltage generating circuit-   112 charging voltage generating circuit-   113 deflection voltage generating circuit-   114 solenoid valve control circuit-   200 filter-   201 capsule member-   202 capsule member-   203 filter medium-   204 cap member-   211 central connecting port-   212 peripheral connecting port-   235 top surface section-   245 bottom surface section (first bottom surface section)-   240 sloped section-   250 deepest section-   301 ink container-   302 ink supply reservoir-   303 solvent supply reservoir-   311 feed pump-   312 circulation pump-   313 recovery pump-   314 solvent pump-   321 solenoid valve-   322 solenoid valve-   323 solenoid valve-   324 solenoid valve-   325 solenoid valve-   326 solenoid valve-   327 solenoid valve-   328 three-way solenoid valve-   331 pressure-reducing valve-   332 pressure gauge-   351 nozzle-   352 charging electrode-   353 deflection electrode-   354 gutter-   360 ink particles

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. It should be noted that thefollowing embodiments are illustrative only for the purpose of carryingout the present invention, and are not intended to limit the technicalscope of the present invention. In addition, structures that are commonto all of the drawings are denoted by common reference numerals.

<External Appearance and Use State of Ink-jet Recording Apparatus>

FIG. 14 illustrates the external appearance of an ink-jet recordingapparatus 100 in accordance with an embodiment of the present invention.The ink-jet recording apparatus 100 includes a main body 1 with anoperation display section 3 externally mounted thereon and an inkdischarge head 2 connected to the main body 1 with a conduit 4.

FIG. 15 illustrates an example of the actual use state of the ink-jetrecording apparatus 100. The ink-jet recording apparatus 100 isinstalled on, for example, a production line of a factory in whichfoods, beverages, and the like are produced. The main body 1 isinstalled in a position where the user can operate the apparatus, andthe ink discharge head 2 is installed in a position that can be inproximity to an object 13 on which text is to be printed (hereinafterreferred to as a print medium 13) that is transported on a productionline such as a belt conveyor 15.

In order to print characters with the same width regardless of thetransport speed, an encoder 16 that outputs a signal corresponding tothe transport speed to the ink-jet recording apparatus 100 as well as aprint sensor 17 that outputs a signal instructing the ink-jet recordingapparatus 100 to print text upon detection of the print medium 13 isinstalled on the production line such as the belt conveyor 15. Suchcomponents are connected to a controller (not shown) within the mainbody 1.

The controller, in response to the signals from the encoder 16 and theprint sensor 17, controls the amount of electrostatic charge and thecharge timing for ink particles discharged from a nozzle, so that theink particles 10, which have been electrostatically charged anddeflected during the passage of the print medium 13 through the vicinityof the ink discharge head 2, are made to adhere to the print medium 13,whereby text is printed thereon.

<Control Configuration of Ink jet Recording Apparatus>

FIG. 16 is a block diagram illustrating the control configuration of theink-jet recording apparatus 100. The ink-jet recording apparatus 100includes, as its control configuration, an MPU 101 that has anarithmetic function and controls the entire ink-jet recording apparatus,ROM 102 that has stored therein programs or data necessary for operatingthe MPU 101 via a bus 120, RAM 103 in which data necessary for theexecution of programs is temporarily stored, an input device 104 intowhich print text information as well as set values is entered, a displaydevice 105 that displays the information entered into the input device104, conditions, and the like, a timer 106 that measures the time thathas elapsed since the given processing, an excitation voltage generatingcircuit 111 that generates an excitation voltage to be applied to adriven element that is mounted on a nozzle 351 for the purpose ofbreaking the ink discharged from the nozzle 351 into particles, acharging voltage generating circuit 112 that generates a chargingvoltage to be applied across charging electrodes 352 for charging inkparticles 360, a deflection voltage generating circuit 113 thatgenerates a deflection voltage to be applied across deflectionelectrodes 353 for deflecting the charged ink particles 360 inaccordance with the print text information, a solenoid valve controlcircuit 114 that controls solenoid valves to be opened or closed toallow the flow of ink or solvent, and a pump control circuit 115 forrotating a motor that drives all of the pumps at a constant speed.

<Filter Structure>

FIG. 8 illustrates the structure of a filter 200 of the ink-jetrecording apparatus 100. The filter 200 has a capsule formed by joininga capsule member 201 and a capsule member 202 together. Within thecapsule is provided a cylindrical filter medium 203. One end face of thefilter medium 203 is joined to the capsule member 201 and the other endface thereof is joined to a cap member 204. The capsule member 201 hastwo connecting ports 211 and 212 that communicate with each otherthrough the filter medium 203.

An opening 221 inside the central connecting port 211 of the capsulemember 201 is located at the center of a dome-shaped top surface section235. Meanwhile, an opening 222 inside the peripheral connecting port 212is located at the end of a pipe-shaped section 230. The capsule member202 has on its inner side a dome-shaped bottom surface section 245 and asloped section 240 that connects the dome-shaped bottom surface section245 to the deepest section 250. It should be noted that the opening 222of the capsule member 201 is located in proximity to the deepest section250 of the capsule member 202 and the distance therebetween ispreferably about 1 to 3 mm.

<Ink Circulation Structure of Ink-jet Recording Apparatus>

FIG. 9 is a systematic diagram of an ink circulation system of theink-jet recording apparatus 100 in accordance with an embodiment of thepresent invention. The ink-jet recording apparatus 100 includes the mainbody 1 and the ink discharge head 2. In the main body 1, the filter 200is disposed in a channel 380 between an ink container 301 and a nozzle351 with a feed pump 311 interposed between the filter 200 and the inkcontainer 301. In addition, a branch 341 leading to a channel 382 thatcommunicates with a suction port of a recovery pump 313 is disposed in achannel 381 between the feed pump 311 and the filter 200. The peripheralconnecting port 212 of the filter 200 is connected to the feed pump 311side and the central connecting port 211 thereof is connected to thenozzle 351 side.

In normal operation, ink stored in the ink container 301 of the mainbody 1 is sucked and pressurized by the feed pump 311 and is transferredto the nozzle 351 of the ink discharge head 2 via the filter 200. Atthis time, a solenoid valve 321 and a three-way solenoid valve 328 areon and the channel between the ink container 301 and the nozzle 351 isopen. In addition, a pressure-reducing valve 331 that adjusts thepressure of ink to an optimum value is disposed in the channel betweenthe feed pump 311 and the nozzle 351, and a pressure gauge 332 thatmeasures the pressure of ink in the channel is disposed in the channelbetween the nozzle 351 and a solenoid valve 324.

Ink that has reached the nozzle 351 is continuously discharged from thedischarge orifice of the nozzle 351. The discharged ink is broken intoink particles 360 by the vibration of the driven element mounted on thenozzle 351. Among the ink particles 360, those used for printing areelectrostatically charged by the charging electrodes 352 and deflectedby the deflection electrodes 353, and then land on a print medium toform text thereon, whereas those not used for printing are not deflectedbut travel into an opening of a gutter 354 that is located along thedirection straight ahead of the discharge orifice of the nozzle 351 andare collected into the ink container 301 by the recovery pump 313 forre-use purposes. At this time, a solenoid valve 325 is on and open.

When ink has been consumed by printing, a solenoid valve 322 is turnedon and placed into an open position to compensate for the consumed ink,whereby ink in an ink supply reservoir 302 is supplied to the inkcontainer 301 via the nozzle 351 and the gutter 354 by the feed pump 311and the recovery pump 313. When the nozzle is not in operation, the inkcan be supplied via the channel in which a solenoid valve 323 isdisposed or the channel in which the solenoid valve 324 is disposed. Theink supply reservoir 302 can be directly supplied with ink from theoutside.

When the amount of solvent in ink has decreased due to volatilizationduring operation, a solenoid valve 326 is turned on and placed into anopen position to compensate for the decreased solvent, whereby thesolvent is supplied to the ink container 301 from a solvent supplyreservoir 303 by a solvent pump 314. The solvent supply reservoir 303can be directly supplied with solvent from the outside.

At start-up of the operation, the solenoid valve 321, the solenoid valve324, and the solenoid valve 328 are turned on and placed into an openposition so that ink in the ink container 301 is circulated into the inkcontainer 301 via the solenoid valve 324 by the feed pump 311 and acirculation pump 312. Accordingly, ink and air that have built up in thechannel between the filter 200 and the three-way solenoid valve 328while the nozzle was not in operation are circulated and the channel isrefreshed.

While the nozzle is not in operation, solvent in the solvent supplyreservoir 303 is pumped into the nozzle 351 by the solvent pump 314, andis discharged from the discharge orifice of the nozzle 351. Accordingly,the discharge orifice of the nozzle 351 is washed with the solvent andink is prevented from building up on or adhering to inner side of thedischarge orifice. At this time, a solenoid valve 327 is on whereas thesolenoid valve 328 is off Thus, the channel between the solvent supplyreservoir 303 and the nozzle 351 is open.

<Ink Removal Operation>

FIG. 10 illustrates the flow of ink in removal of the ink from thefilter 200 of the ink-jet recording apparatus 100. Once the ink removaloperation is initiated, the solenoid valve 323 and the solenoid valve328 are turned on so that the channel 380 between the ink container 301and the nozzle 351, in which are arranged the filter 200 and thesolenoid valve 323, opens, so that ink flows in the direction of anarrow 390. Since the nozzle 351 is exposed to air through the dischargeorifice, ink in the channel 380 is gradually displaced by air. When allthe ink has been removed and displaced by air, the ink removal operationterminates.

FIG. 11 illustrates the orientation of the filter 200 of the ink-jetrecording apparatus 100 in removal of ink from the filter. In FIG. 11,an arrow 400 indicates the upward direction. The filter 200 in theink-jet recording apparatus 100 is arranged such that the centralconnecting port 211 and the peripheral connecting port 212 face upwards.During removal of the ink, the ink flows in the direction from thecentral connecting port 211 to the peripheral connecting port 212 of thefilter 200 as indicated by arrows 410, with the ink flowing in thedirection of the arrow 390 (see FIG. 10). When ink in the channel 380 isbeing displaced by air, the air gradually enters the central connectingport 211 of the filter 200 and the ink is gradually discharged from theperipheral connecting port 212. Finally, ink located above the opening222 is displaced by air, whereby almost all the ink in the filter 200can be discharged.

FIG. 17 is a flowchart illustrating the control operation in removal ofink from the filter 200 of the ink-jet recording apparatus 100. First,in step 801, the pump control circuit 115 drives the feed pump 311, thecirculation pump 312, the recovery pump 313, and the solvent pump 314 inresponse to an instruction indicative of the initiation of ink removaloperation. Next, in step 802, the solenoid valve control circuit 114turns the solenoid valve 323 and the solenoid valve 328 on to place theminto an open position. At this time, air is sucked into the nozzle 351so that ink in the channel 380 is discharged to the ink container 301.

Next, when the timer value has reached a given value K1 in step 803, thepump control circuit 115 stops the feed pump 311, the circulation pump312, the recovery pump 313, and the solvent pump 314 in step 804. Then,in step 805, the solenoid valve control circuit 114 turns the solenoidvalve 323 and the solenoid valve 328 off to place them into a closedposition. Accordingly, the ink removal process terminates.

<Air Removal Operation>

FIG. 12 illustrates the flow of ink in removal of air from the filter200 of the ink-jet recording apparatus 100. Once the air removaloperation is initiated, the solenoid valve 322, the solenoid valve 324,and the solenoid valve 328 are turned on. Then, the channel 383 betweenthe ink supply reservoir 302 and the ink container 301, in which arearranged the filter 200, the nozzle 351, and the solenoid valve 324,opens, so that ink flows in the direction of an arrow 391, and air inthe channel 383 is gradually displaced by the ink.

FIG. 13 illustrates the orientation of the filter 200 of the ink-jetrecording apparatus 100 in removal of air from the filter. In FIG. 13,an arrow 420 indicates the upward direction. The filter 200 in theink-jet recording apparatus 100 is, as in the removal of ink, arrangedsuch that the central connecting port 211 and the peripheral connectingport 212 face upwards. In removal of air, ink flows in the directionfrom the peripheral connecting port 212 to the central connecting port211 of the filter 200 as indicated by arrows 430, with the ink flowingin the direction of the arrow 391 (see FIG. 12). When air in the channel383 is being displaced by ink, the ink gradually enters the peripheralconnecting port 212 of the filter 200 and the air is graduallydischarged from the central connecting port 211. Finally, almost all theair in the filter 200 can be discharged.

FIG. 18 is a flowchart illustrating the control operation in removal ofair from the filter 200 of the ink-jet recording apparatus 100. In step851, the pump control circuit 115 drives the feed pump 311, thecirculation pump 312, the recovery pump 313, and the solvent pump 314 inresponse to an instruction indicative of the initiation of air removaloperation. Next, in step 852, the solenoid valve control circuit 114turns the solenoid valve 322, the solenoid valve 324, and the solenoidvalve 328 on to place them into an open position. At this time, ink issucked from the ink supply reservoir 302 so that air in the channel 383is discharged to the ink container 301.

Next, when the timer value has reached a given value K2 in step 853, thepump control circuit 115 stops the feed pump 311, the circulation pump312, the recovery pump 313, and the solvent pump 314 in step 854. Then,in step 855, the solenoid valve control circuit 114 turns the solenoidvalve 322, the solenoid valve 324, and the solenoid valve 328 off toplace them into a closed position. Accordingly, the air removal processterminates.

<Conclusion>

The upper capsule member of the filter of the present invention has acentral connecting port and a peripheral connecting port. In addition,the upper capsule member has on its inner side a pipe section thatextends from the peripheral connecting port. When the upper capsulemember and the lower capsule member are joined together to form a singlecapsule, the end of the pipe section is adapted to be located inproximity to the bottom surface section (the deepest section) of thelower capsule member. When the filter is to be used with a liquidfiltered therethrough (when air is to be removed), a liquid suppliedfrom the peripheral connecting port via the pipe section is filtered bya filter medium, and the filtered liquid is output from the centralconnecting port. Accordingly, air in the filter can be completelyremoved and the possibility of abnormal printing can be reduced.Meanwhile, when a liquid is to be collected (when a liquid is to beremoved), a liquid remaining in the filter is sucked into the end of thepipe section located in proximity to the deepest section of the filter.Accordingly, it is possible to collect the liquid so that almost noliquid would remain in the filter. Thus, the possibility ofcontamination resulting from leakage of residual liquids can be reducedin replacement of the filter.

An opening inside the central connecting port of the upper capsulemember of the filter is located at the center of the dome-shaped topsurface section. In addition, the lower capsule member has on its innerside a dome-shaped bottom surface section (the first bottom surfacesection) and the deepest section (the second bottom surface section),and also has a sloped section that connects the central portion of thefirst bottom surface section to the deepest section. The provision ofsuch a dome-shaped top surface section allows the air in the filter tobe more completely removed. In addition, since the center of thedome-shaped bottom surface section and the deepest section of the lowercapsule member are connected with the slope, liquid in the filter can beefficiently collected.

When a filter is used in an ink-jet recording apparatus, such a filteris arranged in a channel between an ink container and a nozzle with afeed pump interposed between the filter and the ink container. Inaddition, a branch leading to a channel that communicates with a suctionport of a recovery pump is disposed in a channel between the feed pumpand the filter. The filter is arranged in the ink-jet recordingapparatus such that the central connecting port and the peripheralconnecting port thereof face upwards. Accordingly, upon entry of airinto the central connecting port, ink is discharged from the peripheralconnecting port, and thus, the ink in the filter is displaced by theair. Accordingly, almost all the ink in the filter can be discharged. Inremoval of air, ink flows in the direction from the peripheralconnecting port to the central connecting port. In such a case, air isdischarged from the central connecting port upon entry of ink into theperipheral connecting port. Thus, almost all the air in the filter canbe displaced by the ink.

Although this embodiment has described examples of the application of afilter to an ink-jet recording apparatus, such a filter can be appliednot only to ink-jet recording apparatuses but also to apparatuses ingeneral in which a liquid should be filtered.

What is claimed is:
 1. A filter comprising a first container and asecond container that sandwich a filter medium therebetween, wherein:the first container has a central connecting port and a peripheralconnecting port, a pipe section that communicates with the firstcontainer and the second container and extends to the vicinity of abottom surface of the second container formed inside the peripheralconnecting port, and the second container has on its inner side a firstbottom surface section and a second bottom surface section that isconnected to the first bottom surface section and located opposite andin proximity to an end of the pipe section at a position deeper than thefirst bottom surface section.
 2. The filter according to claim 1,wherein the first bottom surface section and the second bottom surfacesection are connected via a sloped section leading from the centralportion of the first bottom surface section to the second bottom surfacesection.
 3. The filter according to claim 1, wherein the pipe sectionhas a diameter that is smaller than the peripheral connecting port. 4.The filter according to claim 1 , wherein the first container has on itsinner side a domeshaped top surface, and the central connecting port isarranged at the center of the domeshaped top surface.
 5. An ink-jetrecording apparatus comprising: a nozzle that discharges ink used forprinting; an ink container in which the ink is stored; a feed pump thatpumps the ink to the nozzle; a recovery pump that collects the ink intothe ink container; and a filter arranged between the nozzle and the inkcontainer, the filter being adapted to filter the ink, wherein: thefilter includes a first container and a second container that sandwich afilter medium therebetween, the first container has a central connectingport and a peripheral connecting port, a pipe section that communicateswith the first container and the second container and extends to thevicinity of a bottom surface of the second container formed inside theperipheral connecting port, and the second container has on its innerside a first bottom surface section and a second bottom surface sectionthat is connected to the first bottom surface section and locatedopposite and in proximity to an end of the pipe section at a positiondeeper than the first bottom surface section.
 6. The ink-jet recordingapparatus according to claim 5, wherein the first bottom surface sectionand the second bottom surface section are connected via a sloped sectionleading from the central portion of the first bottom surface section tothe second bottom surface section.
 7. The ink-jet recording apparatusaccording to claim 5, wherein the pipe section has a diameter that issmaller than peripheral connecting port.
 8. The ink -jet recordingapparatus according to claim 5, wherein the first container has on itsinner side a dome-shaped top surface, and the central connecting port isarranged at the center of the dome-shaped top surface.
 9. The ink -jetrecording apparatus according to claim 5, wherein a branch is providedin a channel between the feed pump and the filter, the branch leading toa channel that communicates with a suction port of the recovery pump.10. The ink-jet recording apparatus according to claim 5, wherein thefilter is arranged such that the central connecting port and theperipheral connecting port face upwards.